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Old 14th July 2020, 11:46 AM   #401
GodMark2
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Originally Posted by marting View Post
Seems to me the difference between the expected value of 1840 (by calculation assuming TFN rate=0 as it's not given) and the 2000 false negatives in Puppycow's example is quibbling. IE: 18.4% v 20%.
My use of the term "long way" was not in reference to the size of the incongruity, but the possibilities of miscommunication arising from using well-defined terms in an incorrect manner, with the user having emphatic conviction that the incorrect interpretation was correct. This often leads to further misunderstanding as neither side feels the need to specifically define the term, as both believe their definition to be obvious. This can then snowball into further distrust as each side begins to fortify their position, attacking the other side with less and less logic and more and more emotion. Eventually, both sides can end up seeing the other as completely lacking any rational basis.

Cutting off such a path by specifying the exact definitions being used can go a "long way" toward facilitating productive conversation.
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Old 14th July 2020, 12:19 PM   #402
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Originally Posted by rjh01 View Post
That is even worse. The positive results were 3 months apart! That would mean that Covid 19 is a chronic illness. It would also mean that after Australia clears everyone from the virus it could spontaneously reappear, not from overseas but from these cases.
It would also suggest that people who. have had a case confirmed need to be isolated for quite sometime.
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Old 14th July 2020, 12:24 PM   #403
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Originally Posted by GodMark2 View Post
My use of the term "long way" was not in reference to the size of the incongruity, but the possibilities of miscommunication arising from using well-defined terms in an incorrect manner, with the user having emphatic conviction that the incorrect interpretation was correct. This often leads to further misunderstanding as neither side feels the need to specifically define the term, as both believe their definition to be obvious. This can then snowball into further distrust as each side begins to fortify their position, attacking the other side with less and less logic and more and more emotion. Eventually, both sides can end up seeing the other as completely lacking any rational basis.

Cutting off such a path by specifying the exact definitions being used can go a "long way" toward facilitating productive conversation.
I agree. But it would have been best if you had also shown the impact of using proper definitions on the numbers in Puppycow's post. Otherwise, it just leaves many scratching their heads and thinking you are objecting to the major point of Puppycow's post. For example this would be more elucidating in addition to adding the formula and link:

Originally Posted by Puppycow View Post
I just want to add a little bit more to this for clarification after reading more.

A false positive rate of 2% does not mean that 2% of all positive results are false positives, it means that 2% of all tests conducted (both positive and negative) are false positives.
True false positive rate is the percentage of actual negatives that are detected as positives.

Quote:
What this means in practice is that, if say the true rate is 8% and the false positive rate of 2%, then 20% of all positive results are false positives.
Which is 18.4% since the false positive rate only applies to actual negatives falsely detected.

Quote:
The lower the true rate is, the greater the proportion of positive results will be false positives.

So out of say, 10,000 positive tests (out of 100,000 total tests given), 2,000 of those may be false positives.
1840, not 2000, would be the expected number of false positives in the example.

Quote:
Given that, the scenario where someone gets "reinfected" because of a false positive test seems quite likely to occur given enough tests conducted.
Right.
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Old 14th July 2020, 12:27 PM   #404
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Using the wrong formula and arriving at a result sorta close to the one in the correct formula is not laudable or mean that the correction is "quibbling."

No half credit for that.

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Old 14th July 2020, 02:33 PM   #405
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First Dog on the Moon on surviving a second lockdown

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Do remember that the lockdown isn't the problem - the virus is the problem. The lockdown is a seat belt and you are a passenger in a dreadful analogy being driven at high speed by the virus who is probably drunk.
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Old 14th July 2020, 02:33 PM   #406
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"Absence of Apparent Transmission of SARS-CoV-2 from Two Stylists After Exposure at a Hair Salon with a Universal Face Covering Policy — Springfield, Missouri, May 2020"

https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm

Quote:
What is added by this report?

Among 139 clients exposed to two symptomatic hair stylists with confirmed COVID-19 while both the stylists and the clients wore face masks, no symptomatic secondary cases were reported; among 67 clients tested for SARS-CoV-2, all test results were negative. Adherence to the community’s and company’s face-covering policy likely mitigated spread of SARS-CoV-2.
While this seemed compelling back when it was reported, I though it not totally compelling because it's well known that the propensity to spread is highly heterogeneous. Since only two hairdressers had Covid-19 there was a reasonable chance that both were not good spreaders. The CDC report shows that one was. They refer to her as stylist A. All of her 4 close contacts, as well as her co-worker, tested positive for Covid-19.

Quote:
Six close contacts of stylists A and B outside of salon A were identified: four of stylist A and two of stylist B. All four of stylist A’s contacts later developed symptoms and had positive PCR test results for SARS-CoV-2. These contacts were stylist A’s cohabitating husband and her daughter, son-in-law, and their roommate, all of whom lived together in another household. None of stylist B’s contacts became symptomatic.
Highly consistent with masks working when both the infected and uninfected wear them. It provides no info. re the relative efficacy of masks for the infected v the uninfected.
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Old 14th July 2020, 06:50 PM   #407
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Intuitive Biostatistics

Originally Posted by GodMark2 View Post
This would go a long way toward explaining many misunderstandings earlier.
I covered these definitions in comment #2592 of the first thread. Motulsky's book is one worth having.
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Old 14th July 2020, 06:53 PM   #408
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Originally Posted by marting View Post
Highly consistent with masks working when both the infected and uninfected wear them. It provides no info. re the relative efficacy of masks for the infected v the uninfected.
Pity that horse has bolted.

When people are prepared to commit violence, and even murder, over wearing a face mask, you've already lost.
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Old 14th July 2020, 07:53 PM   #409
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More good news on vaccines: https://www.nzherald.co.nz/world/new...ectid=12348208

Still needs more work, but we're making quick progress.
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Old 14th July 2020, 09:25 PM   #410
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Moving to Stage 3 this quickly is pretty impressive. It's important to remember that the first vaccines approved for general use are unlikely to be the most effective. But they'll be better than nothing.
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Old 14th July 2020, 09:46 PM   #411
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Originally Posted by The Atheist View Post
Uh-oh.

That "can you catch Covid again" question may have been answered in the positive.

https://www.vox.com/platform/amp/202...-herd-immunity

tl;dr version:

Guy has mild Covid, recovers & tests negative twice.

Then gets a bad dose, requiring multiple hospital visits.

This would be unbelievably bad news for a second wave, considering the overwhelming majority of people having a very mild/asymptomatic dose in the first wave.

Those shades of 1918 just went up a notch.
He wouldn't be the first, by a long shot? There have been reports of people with repeat cases for quite a while, now, beyond just testing positive again, IIRC. Still, when it comes to concern related to reinfections during a second wave, I would think that the seemingly probable lung scarring from the first case (even in asymptomatic cases) would likely be something to focus on more as a reason for likely worse symptoms if the body's defenses don't remain strong.
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Old 14th July 2020, 10:29 PM   #412
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Originally Posted by GodMark2 View Post
According to Wikipedia, you are exactly incorrect. False positive rateWP


This would go a long way toward explaining many misunderstandings earlier.
Originally Posted by marting View Post
Seems to me the difference between the expected value of 1840 (by calculation assuming TFN rate=0 as it's not given) and the 2000 false negatives in Puppycow's example is quibbling. IE: 18.4% v 20%.
Thank for clarifying that. My statement was incorrect. You have to subtract the true positives from the denominator. However, it still means a larger number than 2% of the positive results. As you say, in my hypothetical example, that would result in 1840, not 2000 false positives.
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Old 14th July 2020, 10:43 PM   #413
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Quote:
Police in the ACT have politely been requesting that people in Canberra stop answering the door in the nude during Covid-19 compliance requests.

In a press conference this morning detective superintendent, Jason Kennedy, said those in isolation had been offering police a “warm reception”.

But, as News.com.au reports, some of the welcomes were a little too friendly; “Some of them may need a reminder to put some clothes on before they open the door for a compliance check,” he said.

“We did get a few surprises on the weekend.

The ACT has again recorded no new cases of Covid-19 on Wednesday.
Source

Go Canberra!
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Old 14th July 2020, 11:55 PM   #414
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Some more data about people with Covid-19 who are asymptomatic

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And the study showed 69% of those who did test positive reported no symptoms on the day of their test or the previous week, though they may have developed symptoms later.
https://www.bbc.co.uk/news/uk-53414363
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Old Yesterday, 12:13 AM   #415
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Originally Posted by arthwollipot View Post
Source

Go Canberra!
I wonder why the police were calling on those houses for? Had they just had a test? What made the residents answer the door in the nude? Was it a show of disrespect or something?
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Old Yesterday, 03:19 AM   #416
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Originally Posted by The Atheist View Post
More good news on vaccines: https://www.nzherald.co.nz/world/new...ectid=12348208

Still needs more work, but we're making quick progress.
And some more:

https://www.itv.com/news/2020-07-15/...-robert-peston

The vaccine is currently in Phase III trials in the UK, Brazil and S.Africa with a large trial due to start in the USA next month.
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Old Yesterday, 07:20 AM   #417
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This report is a comparison between Finland and Sweden, two in many ways similar countries who applied different measures regarding schools during the covid-19 pandemic. There is no difference in the overall incidence of the laboratory confirmed covid-19 cases in the age group 1-19 years in the two countries and the number of laboratory confirmed cases does not fluctuate with school closure or change in testing policy in Finland. In Sweden, the number of laboratory confirmed cases is affected by change in testing policy. Severe covid-19 disease as measured in ICU admittance is very rare in both countries in this age group and no deaths were reported. Outbreak investigations in Finland has not shown children to be contributing much in terms of transmission and in Sweden a report comparing risk of covid-19 in different professions, showed no increased risk for teachers.

In conclusion, closure or not of schools had no measurable direct impact on the number of laboratory confirmed cases in school-aged children in Finland or Sweden. The negative effects of closing schools must be weighed against the positive indirect effects it might have on the mitigation of the covid-19 pandemic.
https://www.folkhalsomyndigheten.se/...d-children.pdf
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Old Yesterday, 11:51 AM   #418
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Originally Posted by Aridas View Post
He wouldn't be the first, by a long shot? There have been reports of people with repeat cases for quite a while, now, beyond just testing positive again, IIRC.
Yes, the defence that the test was faulty the first time is getting pretty hard to accept.

Originally Posted by Arcade22 View Post
Not to mention, none of the studies on schools have taken into account the immense harm done by having kids not at school.
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Old Yesterday, 04:54 PM   #419
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Originally Posted by The Atheist View Post
Yes, the defence that the test was faulty the first time is getting pretty hard to accept.
Why?

If I'm right about this, it seems highly likely that there would be multiple examples of apparent reinfections due to false positive test results. Of course, it's just speculation on my part, but the hypothesis has to be ruled out somehow, and I don't see how it is ruled out.

Anyway, seems like something that could be studied. Can samples be retested by another lab or are they immediately destroyed after being tested?
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Old Yesterday, 05:37 PM   #420
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Originally Posted by Puppycow View Post
Why?

If I'm right about this, it seems highly likely that there would be multiple examples of apparent reinfections due to false positive test results. Of course, it's just speculation on my part, but the hypothesis has to be ruled out somehow, and I don't see how it is ruled out.
I'm going on the now numerous cases of claims of reinfection. People have been trying to explain them away as false positives and/or false negatives, but the more cases there are, the more likely it is actually being reinfected.

Originally Posted by Puppycow View Post
Anyway, seems like something that could be studied. Can samples be retested by another lab or are they immediately destroyed after being tested?
They wouldn't be kept either way, mainly for logistical reasons. Whether they could be re-tested I don't know, but I'm presuming not, because the virus will break down if it gets dry, so you'd be faced with keeping millions of tests and cost would be prohibitive.

It's just something else we need to wait for more work.
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Old Yesterday, 05:46 PM   #421
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Originally Posted by rjh01 View Post
I wonder why the police were calling on those houses for? Had they just had a test? What made the residents answer the door in the nude? Was it a show of disrespect or something?
You know exactly as much as I do. The only time I've ever answered the door in the nude it was someone who was wondering whether I was the owner of the car that had parked him in.
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Old Yesterday, 08:14 PM   #422
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Originally Posted by The Atheist View Post
I'm going on the now numerous cases of claims of reinfection. People have been trying to explain them away as false positives and/or false negatives, but the more cases there are, the more likely it is actually being reinfected.
Why?

Why, as more cases occur, is it more likely to be actual reinfections, rather than false positives which we know for a fact happen?
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Old Yesterday, 08:36 PM   #423
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Originally Posted by The Atheist View Post
I'm going on the now numerous cases of claims of reinfection. People have been trying to explain them away as false positives and/or false negatives, but the more cases there are, the more likely it is actually being reinfected.
I doubt these are reinfections, I think they are Long Haulers
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Old Yesterday, 08:39 PM   #424
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Wouldn't these claims of reinfection have to exceed the false positive rate for it to be more likely that they were real rather than false positives in the first place?
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Old Yesterday, 10:46 PM   #425
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Originally Posted by GraculusTheGreenBird View Post
Why?

Why, as more cases occur, is it more likely to be actual reinfections, rather than false positives which we know for a fact happen?
Simple maths. If more and more people get reinfected, and the longer period between infections, we can be more confident of what's happening.

It will be solved one way or the other in the next few months.
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Old Yesterday, 11:02 PM   #426
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Originally Posted by The Atheist View Post

They wouldn't be kept either way, mainly for logistical reasons. Whether they could be re-tested I don't know, but I'm presuming not, because the virus will break down if it gets dry, so you'd be faced with keeping millions of tests and cost would be prohibitive.
The swabs are sent in viral transport media so they don't dry out. (We do keep ours).
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Old Today, 12:17 AM   #427
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Lots on Long Haulers at the beginning of this episode, including some who seemed to be PCR negative for a bit

https://www.microbe.tv/twiv/?fbclid=..._5oMB1C0P7fXxs
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Old Today, 07:38 AM   #428
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A good NY Times article comparing the various COVID-19 treatments and what is known about their efficacy:
https://www.nytimes.com/interactive/...gtype=Homepage
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